The field of the present invention is product discrimination systems based on sensed light spectra.
Product handling activities for the discrimination of product units have long been used, particularly in the food product industry. Such discrimination has been based on size, ripeness, color, blemishes and the like. Until recent times, this activity was generally undertaken by manual labor. The versatility of workers for handling and processing large amounts and varieties of food products has generally been unsurpassed. Such processing systems generally include conveyor passing working stations where workers were able to distinguish and separate product units. Such labor was generally inexpensive and seasonal. However, difficulties in finding experienced seasonal workers and the normal administrative problems associated with a fluctuating work force have long created a need for less labor intensive systems.
In defining the needs for product handling systems, as particularly applied to the food industry, the nature, volume, relative unit cost and variety of products severely inhibit the design of handling equipment. Most food products must be handled with great care to avoid damage. The perishable nature and large batch quantities of products in season makes rapid processing a necessity. The variety of products which must be processed at different times to economically justify a food processing facility places great demand for versatility on the equipment. Thus, a substantial challenge exists in creating handling equipment to replace the versatile human worker.
An early system for handling of products in a manner acceptable for automatic sorting is disclosed in U.S. Pat. No. 4,106,628 to Warkentin et al. for SORTER FOR FRUIT AND THE LIKE, the disclosure of which is incorporated herein by reference. In this patented device, cups are arranged on a chain conveyor for holding individual product units. Solenoids act to dump selected cups for product separation responsive to discriminating sensing and electronic commands. Other separating systems include devices for batting or blowing selected units from a conveyor.
In the early system of U.S. Pat. No. 4,106,628, color from a product unit is directed through lenses, fiber optics and filters to a sensing mechanism. In the actual system, light from both sides of a product unit was gathered in a single scan per product unit by two bundles of optic fibers looking from opposed sides of the product unit. Each optic fiber bundle was split and combined with a respective split portion of the other bundle. Therefore, each resulting optic fiber bundle had light from both sides of the product unit. Filters of different wavelength capacity were employed to filter the light derived from the resulting two fiber optic bundles. Red and green filters were given as examples, one filter for each resulting bundle. The signals generated by the filtered light were then compared with a standard such that a red/green color classification could have been made based on the readings compared with the standard.
Another system which has been in use for some time is disclosed in U.S. Pat. No. 4,961,489 to Warkentin for PRODUCT HANDLING SYSTEM, the disclosure of which is incorporated herein by reference. In this device, a conveyor is employed which includes elements capable of tipping to off-load individual units of a product being processed. The nature of the conveyor permits some variety in shapes and sizes, including elongated products. However, a range of round or oval products in smaller sizes is not as easily accommodated by this system.
Another system which has been in use successfully for some time is disclosed in U.S. Pat. No. 5,029,692 to Warkentin for OFF-LOADING CONVEYING SYSTEM, the disclosure of which is incorporated herein by reference. In this device, a conveyor is employed which includes concave rollers defining concavities therebetween. Off-loading elements are positioned between adjacent rollers in each of the concavities. The elements are pivotally mounted about pivot axes parallel to the conveying direction and can be actuated to off-load product units away from these pivot axes.
A product discrimination system employing the sensing of a variety of light spectra, which may include wavelengths both in and beyond the visible spectrum, from product units being classified is disclosed in U.S. Pat. No. 5,018,864 and U.S. Pat. No. 5,106,195, both to Richert for PRODUCT DISCRIMINATION SYSTEM AND METHOD THEREFOR, the disclosures of which are incorporated herein by reference. The system has particular utility in sorting food products such as fruits and vegetables. The magnitudes of the sensed light spectra is analyzed to determine such attributes of a product as size, ripeness, blemishes and color. A manageable amount of data is received and processed by such a system with a maximum number of product factors being determined.
In the system of U.S. Pat. Nos. 5,018,864 and 5,106,195, a focused image of a product unit is directed to a fiber optic array. The array has a first end which is arranged in a rectangle. Because of this arrangement, the fiber optic cable receives what approximates a line scan image. The image may be averaged and then divided and directed through filters to provide a plurality of sensed signals for different wavelengths. Intensity may be measured for each selected wavelength spectrum. Consequently, only a few signals, the magnitude of each separately filtered portion of the image, need be processed. Methods for discriminating attributes of product units use absolute magnitudes and comparative relationships between magnitudes of various spectra of light sensed from a product unit to determine such attributes as size, color, ripeness and blemishes. Such methods may be carried out on a variety of sensing hardware including line scan cameras as well as the fiber optic system of the preferred embodiment. Even a combination of such systems was suggested.
More complicated sensing devices have been developed which use line scan cameras for determining such attributes as cross-sectional area. Such cameras have used light to present pixel information which may then be processed for summation and the like. For example, cross-sectional area may be determined by counting the number of pixels registering presence of the product unit. Such systems collect information in the form of pixel location, color or colors, and intensity, generating a substantial amount of data to be received and processed.
A system used with such off-loading conveyors for discriminating product units is disclosed in U.S. Pat. application No. 479,107, filed Feb. 13, 1990, to Warkentin et al. for PRODUCT DISCRIMINATION SYSTEM AND METHOD THEREFOR, the disclosure of which is incorporated herein by reference. A fiber optic system is used to sense physical attributes of the conveyed product units. A system for rotating the fruit between sensors provided added accuracy. Multiple sensing of the product is accomplished in series with a partial rotation of the product unit between each sensing and with the product stationary during each sensing. The rotation is accomplished by driving the supporting elements on the conveyor. Such rotation and multiple sensing provides substantial capabilities in the accuracy and variety of measurements derived from the process. An extended drive is provided for rotation of the supporting elements and, in turn, the product units on the conveyor prior to the sensing operation. Fruit and vegetable product units tend to be nonuniform and difficult to singulate and properly position on a conveyor. The rotation of such product units on the supporting elements tends to allow them to properly orientate, seat in a conveyor cavity and separate one from another such that sensing is enhanced.